A winding method and a winding machine of the generic kind have been disclosed in the unexamined laid-open patent application DE 29 07 848 A1 (related to U.S. Pat. No. 4,216,920). Winding machines are used to wind up continuously advancing yarns into bobbins. For this purpose, the yarns are first traversed by a traversing device transversely to the running direction of the yarn and guided over a rotating contact roller. The contact roller places each of the yarns on the likewise rotating bobbins that are to be wound up. A plurality of bobbins is disposed in mutual alignment and one after the other on a common winding spindle. It is thus possible to wind up several yarns simultaneously.
For changing the bobbins automatically, the winding machines are designed with several winding spindles, which are mounted in a projecting manner on a spindle support, which can rotate about an axis. The winding spindle is swiveled alternately into a winding range and into a doffing range by rotating the spindle support. Each yarn is wound up on the tube of a bobbin in the winding range. After the bobbin is wound completely, the winding spindle is swiveled into the doffing range by means of the spindle support. The rotation of the spindle support causes the winding spindle equipped with empty tubes to simultaneously swivel out of the doffing range into the winding range. The yarn, which is still advancing before the bobbin, thus comes into contact with the other winding spindle, which is already rotating in this phase. Catch elements, which catch the advancing yarn, are provided on the winding spindle or on the empty tubes. This winding spindle now winds up the yarn. The yarn connection between the two winding spindles is cut off or torn off using cutting means during this process. The full bobbin is then replaced with an empty tube in the doffing range. During the doffing process described above and immediately before the separation of the yarn connection between the completely wound up bobbin and the tube to be wound up, the yarn accumulates on a defined portion of the completely wound bobbin. This results in a yarn bead, which is considered to be the conclusion of the winding of the bobbin.
The reliability of the yarn changing process, in particular, is at the focal point of all considerations when developing winding machines. Firstly the catch element and secondly the yarn guide are factors relevant to the yarn changing process.
It is known from the prior art to either integrate the catch element into the tube or to provide the same on the winding spindle. Integrating the catch element into the tube implies tubes that require complex manufacturing processes and are therefore more expensive. However, in the case of a catch element provided on the winding spindle, the yarn requires stronger deflection since the catch element is located further outside the traversing range of the yarn. It is disclosed, for example, in the unexamined laid-open patent application DE 25 40 853 A1 (related to U.S. Pat. No. 4,019,690) to displace the winding spindles axially instead of deflecting the yarn strongly. However, as a result of increasingly long winding spindles designed to receive an ever increasing number of bobbins and also as a result of ever increasing winding speeds, it is no longer possible to implement this solution in modern winding machines requiring high levels of rigidity and having bearings that are free of play.
The invention disclosed in DE 29 07 848 A1 provides a plurality of yarn-guiding elements to axially deflect the yarn to a sufficient extent during the yarn changing process and at the same time to firstly guide it perpendicularly to the axis of the winding spindle over the catch element and secondly guide it within the traversing range on the completely wound bobbin. This is a first yarn-guiding element, which is disposed before the catch element and which guides the yarn out of the traversing range and into the range of the catch element. Furthermore, a second yarn-guiding element is disposed behind the catch element in the running direction of the yarn. After the first yarn-guiding element has guided the yarn out of the traversing range, the second yarn-guiding element guides the yarn into the sphere of action of the catch element. Finally, a third yarn-guiding element is disposed in such a way behind the second yarn-guiding element, when seen in the running direction of the yarn, that the yarn is guided back into the traversing range.
The guidance of the yarn in the yarn catching process is of special importance in connection with high winding speeds. This is firstly because the reliability of catching the yarn reduces as the winding speed increases. Furthermore, as an aggravating factor it has to be added that the lesser reliability in catching the yarn cannot be compensated by a higher dwell time in the range of the catch element since a large amount of yarn accumulates in this range very rapidly. Rather, it would be actually necessary to reduce the dwell time in the range of the catch element as the winding speed increases, thereby resulting in a conflict of objectives.
It is therefore an object of the invention to improve the reliability of catching the yarn using the winding machines known from the prior art.